Off grid cabin without batteries

[73powerstroke]

IME, the only thing I would run off PV directly are things designed to, like a PV water pump. I can charge my cell phone off a 100 watt panel and a buck converter to stabilize the voltage, but a half amp at 24 volts charging is not a lot.


Bigger than tiny wattages becomes an issue as power starts to cycle on and off for clouds and surges. Comes down to, is the equipment able to stand this or not? I would not want to hook something to this.

There is not a single commercial off the shelf, off grid application for a solar generator without a battery. Not one. If you dig deep enough on YouTube you will find one, but they are not longer in business.

There’s been a lot of brainpower put into these projects by DIY communities, but never has it been successfully done, at least to a standard of living in a house like a running AC. There is Will’s video where he is able to run an AC off solar directly, but this is not left on all day long, only shows it running for a minute.

I have a solar 300 watt generator with a small battery pack, started with around 600 wh of batteries, with these batteries acting as a buffer for these cloudy events. You can do a lot with a “reduced” battery pack with less capacity operating towards peak output, if you can go without power or have backup for several days but run large loads during the sunshiny days.

 

[mvonw]

I recently built an off grid 500 square ft cabin in the mountains and I'm looking to install some solar on a relatively tight budget. The cabin is unattended for months at a time and can get down to -20F in the winter, so I would really like to avoid leaving large batteries there (I would also like to avoid the expense). The cabin has a wood stove for heat, so the main electrical loads would be a heat pump (primarily for cooling in the summer), minifridge, 1-2 burner cooktop, and small lights. I also hope to eventually add an EV charging station. It's insulated nearly to passive house standards, so I imagine there would be no problem running cooling systems only when the sun is out. Cooking and EV charging could also be adjusted to accommodate the sun. I figure roughly 3-4kW of solar would allow level 1 EV charging plus other loads when the sun is out.

I'm thinking of using Enphase microinverters to allow for a modular system. With microinverters on each panel, could the panels be wired straight to a breaker box or would I need any other electronics in between?

I realize that power will shut off briefly every time a cloud passes. Are there any problems associated with supplying appliances and EV chargers with intermittent power? I'm worried the contactors on the EV will wear out if they are frequently switching between open and closed. Also not sure how it would affect heat pumps or other appliances.

Will there be a big voltage drop when a load is turned on? Would this cause the load to detect a power supply failure and stop charging? This is what happened when I tried to wire my 12V Dewalt tool battery charger straight to a solar panel, and the charger wouldn't give power to the batteries. I imagine without an intermediary battery the voltage will drop anytime a load is connected. Is this still the case with microinverters on each panel/is there any way around this?

I'm a college student with a few EE classes under my belt but still have a lot to learn. Any advice is much appreciated!

EDIT: Based on the responses, seems like I'll need battery storage at least for an hour or so of use to prevent voltage drop and provide steady output with clouds. I'm hoping to keep the budget under $10k for the system if possible (without including loads/appliances). If I'm using a battery, it seems like microinverters are not the way to go. What are your thoughts on running everything off a single large inverter, vs DC appliances that run directly from the battery with possibly a smaller 2-3kW inverter to power the EV charger? Also, for the size battery that I'm looking at (probably in the 3kWh range) would it be worth it to spend +/- $1000 on a root cellar to keep lithium batteries happy, or should I just go with SLA? Any recommendations for good batteries? Anyone have experience storing lithium batteries underground? Thanks so much for the help!

I considered the underground (root cellar) approach for battery storage (My cabin get similar temps to yours), but realized it wasn’t practical or cost effective. IF you were on the side of hill you could excavate into, it might be more practical. The issue with digging down is usually groundwater and moisture control in general. Batteries are not going to like wet, humid environments. I built a small, super insulated shed for my batteries. Everything in the mountains up north is about winter, so you have to design around those constraints. My solar array and battery bank is way bigger than I really need for 3 season use, but winters are just brutal sometimes.

My advice: Finish school, then get a job and save some money and do it right.

 

[12VoltInstalls]

Maybe instead of a large bank of expensive lithium batteries, a couple of inexpensive lead acid batteries?

It might be possible but the headaches would likely be endless.

It's pretty clear that I was warning the OP that going off grid without batteries is a non-typical application and it's likely going to be more trouble than its worth

Actually no it wasn’t clear; your post below followed the suggestion of lead acid which appeared to me to be response to that.

. Now, almost a week later, you're telling me (why not the OP??) that batteries aren't a problem.

I was lending my opinion to the OP - I wasn’t telling you anything.

Um... so I agree with you "empirically". Did I use that word right? Please take your grievances up with the OP since we're on the same side.

I don’t have a grievance, just trying to help. I think a battery buffer would benefit OP and even though he’s talking a fairly substantial system - for limited buffer use, low cost, with no concern for low temperature I thought the suggest of a small battery bank was a good one.

I would not want to hook something to this.

There is not a single commercial off the shelf, off grid application for a solar generator without a battery. Not one. If you dig deep enough on YouTube you will find one, but they are not longer in business.

This member has a lot of experience doing practical things with a modest system and his guidance seemed appropriate as usual.

Empirical is a word I used colloquially that is represented by this definition fairly well, “capable of being verified or disproved by observation or experiment”

 

[chrisski]

This member has a lot of experience doing practical things with a modest system and his guidance seemed appropriate as usual.

Empirical is a word I used colloquially that is represented by this definition fairly well, “capable of being verified or disproved by observation or experiment”

I might not have been specific who I was referring to. There is nothing out there to reliably run a heat pump off grid without batteries.

Many of us get into this hoping for that, but no one has succeeded in running a high wattage item like a heat pump continuously, day after day, week after week. No one has succeeded. The power interruption from clouds and surges can’t be overcome unless a battery is used as a buffer.

A high wattage item like a hot plate maybe, but not a heat pump.

I’m not arguing the fact that battery-less inverters exist, they do. My earlier statement was incorrect. They can run ACs, until a cloud goes overhead. Then it becomes more of a can the device handle power cycling on and off at peaks dozens of times a day.

 

[ArtDeco]

I recently built an off grid 500 square ft cabin in the mountains and I'm looking to install some solar on a relatively tight budget. The cabin is unattended for months at a time and can get down to -20F in the winter, so I would really like to avoid leaving large batteries there (I would also like to avoid the expense). The cabin has a wood stove for heat, so the main electrical loads would be a heat pump (primarily for cooling in the summer), minifridge, 1-2 burner cooktop, and small lights. I also hope to eventually add an EV charging station. It's insulated nearly to passive house standards, so I imagine there would be no problem running cooling systems only when the sun is out. Cooking and EV charging could also be adjusted to accommodate the sun. I figure roughly 3-4kW of solar would allow level 1 EV charging plus other loads when the sun is out.

I'm thinking of using Enphase microinverters to allow for a modular system. With microinverters on each panel, could the panels be wired straight to a breaker box or would I need any other electronics in between?

I realize that power will shut off briefly every time a cloud passes. Are there any problems associated with supplying appliances and EV chargers with intermittent power? I'm worried the contactors on the EV will wear out if they are frequently switching between open and closed. Also not sure how it would affect heat pumps or other appliances.

Will there be a big voltage drop when a load is turned on? Would this cause the load to detect a power supply failure and stop charging? This is what happened when I tried to wire my 12V Dewalt tool battery charger straight to a solar panel, and the charger wouldn't give power to the batteries. I imagine without an intermediary battery the voltage will drop anytime a load is connected. Is this still the case with microinverters on each panel/is there any way around this?

I'm a college student with a few EE classes under my belt but still have a lot to learn. Any advice is much appreciated!

EDIT: Based on the responses, seems like I'll need battery storage at least for an hour or so of use to prevent voltage drop and provide steady output with clouds. I'm hoping to keep the budget under $10k for the system if possible (without including loads/appliances). If I'm using a battery, it seems like microinverters are not the way to go. What are your thoughts on running everything off a single large inverter, vs DC appliances that run directly from the battery with possibly a smaller 2-3kW inverter to power the EV charger? Also, for the size battery that I'm looking at (probably in the 3kWh range) would it be worth it to spend +/- $1000 on a root cellar to keep lithium batteries happy, or should I just go with SLA? Any recommendations for good batteries? Anyone have experience storing lithium batteries underground? Thanks so much for the help!

I am new here but I didn't notice where you get your water or how you heat it among your loads. I want running water, flush or composting toilets, and (at least) warm showers at the top of my required list...

 

[efficientPV]

I just bought a Bosch ES4 4 gallon water heater from a liquidator in ebay for $48 shipped US. It was brand new in the box, It had been opened and they changed their mind. Stores can't sell anything which has been opened. normally discounted for $217. Putting two in series would still be a deal. I'm going to supplement my 13 gallon tank with this as the primary as this has lower heat loss. 4 gallons only takes 600WH to heat up and way less if it is somewhat warm. I only have a 60V array and have no problem heating water with 120V elements, this one is 10 ohms. You will need a controller for it.

 

[ArtDeco]

I had a 6 gal water heater in my campervan and It would take twice that for my wife to just wash her hair, unfortunately. So I will have to come up with more hot water than that (without heating it on the wood stove).